OPTIMAL CONTROL OF A PNEUMATIC CYLINDER

Abstract

In order to achieve high speed driving and accurate positioning of a pneumatic cylinder, the optimal control method has been applied to a pneumatic servo-system composed of a cylinder, electro-pneumatic proportional valves of pressure type and feedback equipment. State and output equations for the control system were formulated and a quadratic performance function was introduced to obtain optimal feedback coefficients. Optimal regulators, namely control inputs have been computed by a microcomputer without any hardware controller using optimal feedback coefficients which are determined from Riccati's equation so as to minimize settling time of step response in positioning the cylinder. Experimental results show that positioning accuracy is about ±0.2 mm for optimal control and about ±0.1 mm for optimal control with integral compensation at a mean velocity of about 200--300mm/s. These results are compared with those of classical RI control. As a result, the optimal control method, especially optimal control with an integral compensator, is much better in controlled deviation and stability than the PI control method.